Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

470
FXUS63 KLOT 132333
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
633 PM CDT Wed May 13 2026

.KEY MESSAGES...

- After a relatively cool Wednesday, temperatures will trend
  upward through the weekend and into early next week.

- Chances for periodic showers and storms will return to the
  area Thursday night and last through early next week. Some
  storms may be severe, particularly Saturday through Tuesday.

&&

.DISCUSSION...
Issued at 1234 PM CDT Wed May 13 2026

Regional satellite imagery early this afternoon shows expansive
cyclonic flow across the Great Lakes associated with a surface
low pressure system moving across southern Ontario. The passage
of an upper-level shortwave embedded within the parent trough
over southern Lake Michigan allowed for a lake breeze to shift
well inland this afternoon, which is leading to a gradient in
temperatures ranging from the lower 60s west of I-39 to upper
40s along the shore. When combined with blustery north to
northwesterly winds, it feels more like March than May outside
(though the largely sunny skies are welcome).

Tonight, a surface high pressure system will quickly move into
the region causing surface winds to become nearly calm and skies
to clear. Temperatures will hence be poised to plummet
overnight with lows expected to bottom out in the upper 30s to
lower 40s. Patchy frost may develop in the typical cold spots by
daybreak.

The surface high pressure system will only slowly shift away
from the region throughout the day on Thursday, leading to
fairly calm winds. Mostly sunny skies and a gradual increase in
low-level warm air advection will help highs rise into the upper
60s to lower 70s. The exception will be along the Lake Michigan
shoreline where a lake breeze will hold temperatures in the low
to mid 50s.

Thursday night onward:

Toward the end of the week, the upper-level pattern will
transition from predominantly upper-level cyclonic flow across
the northern United States to zonal and eventually
southwesterly flow. The net result will be a gradual warming and
moistening trend leading to more seasonable to above-average
temperatures and periodic shots of showers and storms. Note that
some storms could be severe in the general region, particularly
Saturday through Tuesday. Ensemble guidance suggests a break in
the warm and stormy pattern toward the middle of next week.

Borchardt

&&

.AVIATION /00Z TAFS THROUGH 06Z FRIDAY/...
Issued at 633 PM CDT Wed May 13 2026

VFR conditions are forecast through the period. Any lingering
mid-high clouds will gradually erode with sunset along with
winds becoming light and variable as surface high pressure
settles into the region. Winds return to a light northeast
direction near the lake late Thursday morning then turn east
behind a reinforcing lake breeze. Light and variable winds
continue for inland areas for much of the day before settling
into a prevailing light SSW to SSE direction late in the
afternoon. Increasing high clouds are then expected toward the
end of the period as our next weather system approaches the
area.

Petr

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 1 AM CDT Thursday for the IN
     nearshore waters.

&&

$$

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